Temper Terminology for Copper Alloy Rod and Wire

Created at : Jan 28, 2025

Temper Terminology for Copper Alloy Rod and Wire

What does “temper” mean relative to copper alloy rod manufacturing and applications.
-Temper designations tell both the producer and the user how the alloy has been mechanically and/or thermally treated to achieve the properties desired.
- Temper Designations were designed for AWS (American Welding Society) / RWMA (Resistance Welding Manufacturing Alliance) Electrode Materials.
- Copper alloys used as electrode material for resistance welding, aka, spot welding,  applications are defined in the American Welding Society standard AWS J1.3/J1.3M:2020 by RWMA Class where electrical conductivity and hardness define the temper from Class 1 though Class 22.
- The ASTM temper alpha-numeric  designations defined in ASTM B601 are  not  needed to specify a temper for these materials  as the temper condition is defined by the Class in terms of hardness  and electrical conductivity.
- There are  some cases for Class 3 and 4 materials, typically beryllium copper alloys, where these materials also have ASTM (American Society for Testing and Materials) requirements for TF00 thru TH04, but the property specification requirements are not the same. 
- ASTM temper designations need not and should not be specified concurrently with AWS / RWMA Class numbers (example C15000, C18150, C18200,....).

Historical Perspective

ASTM B601 Temper Designations for ASTM specified copper alloys.
Before 1974, copper alloy tempers were specified as Soft, ¼ hard, ½ hard, full hard, extra hard, spring temper, etc.
The  mill process metallurgist would define the mill process for rod/ wire products based on the B&S gauge numbering system as below. 
 

These apply to copper alloys that harden by cold working.
•    1/4  Hard meant one(1) B&S * gauge number or 21% reduction in area after an in-process softening heat treatment , aka, anneal 
•    1/2  Hard meant two(2) B&S* gauge numbers or 37 % reduction in area after an in-process softening heat treatment , aka, anneal 
•    Hard or Full hard   meant four(4)  B&S* gauge numbers or 60% % reduction in area after an in-process softening heat treatment , aka, anneal
•    Extra Hard  meant six(6) B&S* gauge numbers or 75 % reduction in area after an in-process softening heat treatment , aka, anneal
In 1974, ASTM B601 began to code temper by alphanumeric designations.  
For  work hardening  copper alloys:
•    H01    ¼ hard
•    H02    ½ hard
•    H03    ¾ hard
•    H04    Hard
•    H06    Extra hard
•    H08    Spring 
 Note: It is  interesting that the number in the “H” code still represents the B&S numbers explained above, i.e., H04 mean four(4) B&S numbers hard 
* Brown and Sharpe

For copper alloys that harden by heat treating or a combination of cold working and heat treating, a new set of codes were established ASTM B601.
Precipitation hardening alloys achieve their properties with two heat treatments:
•    Solution heat treat by heating to an elevated temperature and cooling very fast, i.e., quenching in water… this produces a solid solution of two or more different metal phases.  Solution Heat treated material is coded as TB00
•    Precipitation heat treat follows a solution heat treat at a later point in the process, a lower temperature heat treatment where a second metallic phase precipitated into fine particles and hardens the material.  Precipitation heat treated material is coded as TF00 . In the old days this was  specified as AT by manufacturers. For material that is cold worked between the solution anneal and precipitation anneal they may be named to show the amount of cold work used in the process, 
i.    TH01    ¼ hard and heat treated
ii.    TH02    ½ hard and heat treated
iii.    TH03    ¾ hard and heat treated]
iv.    TH04    full hard and heat treated 
It  is noted that these designations are specified in other ASTM material specifications to specifically show the properties of that temper in terms of tensile properties, hardness, and electrical conductivity.
Notable Exception 
Copper alloys used as electrode material for resistance welding, aka, spot welding applications are named in the American Welding Society standard  AWS J1.3/J1.3M:2020 by RWMA  class where electrical conductivity and hardness define the class from Class 1 though Class 22.
The ASTM temper designations defined in ASTM B601 are  not  needed to specify a temper as the temper condition is defined by the Class which is defined  by minimum required properties, hardness, and electrical conductivity.
There are  some cases for Class 3 and 4 materials, typically beryllium copper alloys,  where these materials also have ASTM counterparts of TF00  thru TH04 , but the property specifications are not the same . ASTM temper designations need not and should not be specified concurrently with AWS / RWMA Class numbers.

https://www.astm.org/b0601-18a.html